WheatNews Sept 2019

WHEAT:NEWS SEPTEMBER 2019 Volume 10, Number 9

Hurricane Tribute to Ham Operators

A special thanks to our fellow ham operators with Hurricane Watch Net who provided essential communication to the National Hurricane Center during Hurricane Dorian. Wheatstone’s factory is located a few miles inland from downtown New Bern, North Carolina, a popular destination for hurricanes. (Our factory is on high land but a few of our staff members are still rebuilding from last year’s Hurricane Florence, which hit about this time last year. Read about it in We Survived Hurricane Florence!) We appreciate the ham community and all our broadcast friends who go above and beyond during these times of crisis.

Processing for Streaming

The pyramid of conflict says you can have good, cheap or fast, but not all three.

Streaming is a textbook case of this. We have seen data transfer rates rise and connectivity prices fall, which recently got us wondering about streamed music quality.

We wondered: Could we combine what we know about AoIP with what we know about on-air audio processing to improve the quality of streamed music? Could we give streamers a fuller sound and bring out those crisp highs, that deep bass like we’ve been able to capture with our new X5 FM/HD audio processor? And, could we then push all that through a codec whose job is to lose as many bits as the pipe can handle, often indiscriminate of which ones?

We not only could, but we did. StreamBlade was introduced at IBC this month as a multi-stream appliance for our WheatNet-IP audio network that has selectable Opus, AAC and MP3 encoding and AGC, peak limiter and other processing tools specifically designed to optimize the sound quality of encoded audio content.

It turns out that with the right amount and type of audio processing, you can play to the psychoacoustical characteristics of lossy codecs to get that fuller sound, crisp highs and deep bass. Here are six things to keep in mind.

1. Aggressive time constants can interfere with the codec. “Fast time constants (compression) adds intermod products which the codec has to spend bits on instead of the signals that are actually part of the program. That can be bad for any stream, but it’s especially bad for low bitrate streams that don’t have a lot of data bits to begin with,” said Jeff Keith, Senior Product Development Engineer for Wheatstone’s audio processing line.

Unlike the conventional approach of applying multiband gain control followed by fast compression to build uniform loudness and density from one music source to the next, StreamBlade uses RMS density calculations in its five-band AGC design to invisibly smooth out source transitions and to feed the encoder a steady diet of consistent audio levels.

2. Overshoot is a problem. You’ll need a good limiter. The encoder will not accept any signal over 0 dBFS. You’re out of bits at that point. The best practice for most codecs is to not go over -3 dBFS on the input to the encoder. Even then, you’re going to run out of headroom on some peaks and that’s why a limiter is necessary, to make sure overshoots don’t ever get close to 0 dBFS. But be careful. Not any old limiter will do. According to Keith, aggressive limiting byproducts such as ‘pumping’ and intermod are never good, but they’re especially problematic for encoded audio because the codec can multiply their effect at the expense of regular programming content.

StreamBlade uses a two-band final limiter developed specifically for streaming applications, or what Keith calls the “peak unsquashed final limiter.” “It’s not density control. It’s just peak control, so you have an input to a codec that is pretty darn friendly, even at low bitrates.”

3. Clipping. Nope. Just nope. “The problem with clipping as a peak control mechanism is that it creates harmonics that weren't in the original program and the encoder doesn’t know any better and throws bits at it,” said Keith. Not only is there not enough bit-budget for clipping byproducts, but those byproducts can sound much, much worse once the codec algorithm gets a hold of them. The good news is that streaming doesn’t come with the pre-emphasis can of worms that got broadcasters into heavy clipping to begin with, so clipping isn’t necessary to keep streamed overshoots in check. A good limiter should suffice.

4. Stereo, not so much. Big swings in L-R can trick the codec into disproportionately applying too many bits to L-R data rather than listenable program content. Keeping stereo separation consistent and steady can give you the perception of stereo, but without setting off the encoder. For very low bitrates, monaural might be the best answer as the codec will spend most of its precious bits on listenable content instead of stereo data. Adding a slight boost in bass offers some depth to those monaural programs that are streamed at lower bitrates especially.

StreamBlade has onboard a stereo width management section that eliminates the big swings in dynamic L-R that can skew the codec algorithm in favor of L-R over original content. It also offers bass boost and monaural bass features for optimizing low bitrate streams.

5. Don’t forget noise filters, EQ dynamics, and vocal correction. Streamed programming can often benefit from EQ adjustment, especially at low bitrates. And like broadcast audio, it will require some noise filtering and asymmetry correction on vocals to make the most of the listening experience.

StreamBlade has a two-stage phase rotator to correct voice asymmetry, selectable high- and low-pass filters for removing noise and hum, and four-band parametric equalizer with peak and shelf functions for streaming the best quality as possible on a variety of bitrates.

6. Native IP audio is good. The beauty of AoIP is that you can take music programming straight from the playout system on out to air (or stream) without stepping through A/D/A conversions. A bump in program quality is one of the more important benefits of installing an AoIP system, so why not extend that benefit to your streams as well?

As an AoIP appliance, StreamBlade accepts eight input sources of native WheatNet-IP audio directly from a soundcard or AoIP driver, each capable of four outputs for a total of 32 total output streams.

With all that streaming in one box, it seems StreamBlade is also hitting on another of the three pyramids of conflict: affordability.

Showstoppers

StreamBlade and SwitchBlade win BEST OF SHOW awards at IBC 2019!

Wheatstone won a BEST OF SHOW Award from Future Publishing's Radio World International at IBC 2019 for our new StreamBlade! We ALSO won a BEST OF SHOW Award from Future's PSN Europe for our SwitchBlade!

Look for the Wheatstone banner at the upcoming NAB Radio show in Dallas and the CCBE in Toronto this month!

Also, Steve Dove, one of our key developers on the X5 FM/HD audio processor, will be talking Innovations in Audio Processing at a panel discussion on the subject during AES New York 2019. You won’t want to miss it!

Turning TV Spectrum into AoIP Workflows

Audio Technologist Jonas Bowen, right, is always thinking up new AoIP workflows for WLVT-DTV’s facility, which happens to sit next to the only surviving steel blast furnace in the United States that still has triple pass stoves (shown, above, is the Bethlehem Steel blast furnace in the background).

Nothing like an FCC spectrum auction to brighten up a news facility.

WLVT-DTV of Bethlehem, Penn., spent a portion of its spectrum proceeds on a new WheatNet-IP audio networked studio and Dimension Three Touch console surface and it’s been one shining example after another why IP audio makes so much sense today.

This is the pubcaster’s first foray into IP audio, and with it comes an IP routed console that has tentacles into its three main news studios. On a typical day, operators can track a news interview being recorded on the fly in Studio A, then jump to an event taking place in Studio B – complete with a presenter and PowerPoint with embedded videos going seamlessly over the house speakers. Then, from the same Dimension Three console, they can drop in feeds from local dignitaries seated in Studio C for a satellite shoot with CNN, FOX or MSNBC.

The console brought new workflows for WLVT-DTV, also known as PBS39, which serves the Greater Lehigh Valley in Eastern Penn. and Western New Jersey. But the biggest game changer proved to be the I/O access and specialty units that make up the WheatNet-IP audio network known as BLADEs.

Need a simple HD/SDI de-embedder or a routable mic processor? WLVT-DTV has a BLADE for that. Shown, a few I/O BLADEs racked up in WLVT-DTV’s rack room.

Take the ArtsQuest complex next to the studios that has held many events over the years. In 2011, contractors set up an Ethernet pipe between the two buildings but had never connected both sides. “In May, we brought in a multi-channel Mic BLADE (MP4IP four-channel mic processor as part of the WheatNet-IP network) to the arts complex and finally connected the buildings. We used the fiber haul for the cameras and the Mic BLADE for the audio. We were able to produce the Athlete-of-the-Year event, live, no audio delay, no problems,” said Jonas Bowen, WLVT-DTV ‘PBS39’ Audio Technologist.

Another specialty BLADE, known as the HD/SDI de-embedder BLADE, effectively integrated de-embedding of the audio channel directly into the Dimension Three console. That alone eliminated extra wiring and the breakouts needed with the old AES de-embedder.

Small conveniences count for a lot too, like a USB input into the Dimension Three for playing newsclips and a 5.1 spill feature that makes it easy to isolate any of the eight SDI audio channels coming from the PBS satellite. “’5.1 quality control in a button’ is what we like to call it,” said Bowen.

Overall, he added, “We have gone from the routing cages and crossover cables of 2011, to one rack unit audio over IP control!”

SNMP in the Armed Forces

They now know that the July 13 New York City power outage was due to a flawed equipment connection in one of the electrical substations.

Had they known sooner that there was a problem between the sensors and protective relays at the 65th Street substation, the transformer fire that kept 70,000 New Yorkers in the dark for three hours could have been avoided.

Which brings us to SNMP and our recent email exchange with Zachary Brockett, CSTE and CBNE with Taft Broadcasting Co., LLC, and a systems contractor for Armed Forces Network (AFN).

By anyone’s definition, AFN is one of the world’s most distinguished broadcast operations with radio and television stations around the globe. No one wants to have to tell the AFN brass a flawed anything brought down AFN’s Broadcast Center/Defense Media Center in Riverside, Calif., from where global radio and television satellite feeds emanate.

Enter SNMP, which Brockett uses as part of his toolkit to determine issues before they cause real problems down the line. “I tend to think of SNMP as a nice alert system before needing to delve in with the other tools I typically use,” he said.

SNMP is a well-established set of standards for monitoring and managing data on servers, printers, hubs and switches. Transmitter manufacturers like Nautel and makers of remote-control gear like Burk provide SNMP monitoring in their products. So do AoIP manufacturers like Wheatstone. SNMP has been part of the WheatNet-IP audio network since we introduced the first version of our AoIP system in 2008.

For example, the BLADE I/O access units that make up the WheatNet-IP network each have a unique MIB file of data points, and each BLADE has a unique object address in the network for SNMP monitoring and alerting purposes.

MIB is short for Management Information Base and these files can tell you a lot about the operation of the network, such as bitrates and temperatures of devices or if a particular data stream running across the network is robust or not.

Brockett uses these files to monitor overall system health, starting at the WheatNet-IP audio network BLADEs in the AFN Broadcast Center where multicast streams originate. He monitors the delivery of streams into Cisco switches, and through a common SNMP command (TRAP), an alert is generated when the multicast streams fail to meet certain parameters over a short interval of time. By sending a TRAP message, a client device can alert the SNMP manager to a device that’s overheating, a router port that’s no longer responding, and conditions such as packets that are slowing down.

SNMP also can be used to control anything with a contact closure or logic (like a BLADE), which makes it useful for preemptively changing a signal route if a connection is broken or there’s a problem upstream. In the case of AFN, if packet rejects and drop counts start to rise above a set threshold, the source in question is automatically rerouted to an alternate path.

For overall network infrastructure monitoring, Brockett uses PRTG. This is a very powerful SNMP monitoring application that can visually recreate the network topology to monitor the health of network routers and switches, and keep track of management configurations, VLANs, subnets, and admin duties such as user access and login failure attempts.

For troubleshooting and looking at the network on a more microscopic level, he uses Wireshark – which can also read SNMP commands and MIB files – along with NMAP, FFMPEG, NODE.js scripts and others.

In addition to WheatNet-IP devices and network servers, hubs and switches, the Evertz Dec32 servers in use at AFN (for bringing in multiple IP sources) also use SNMP for monitoring audio volume thresholds and also silence detection, as does the Evertz MVP Multiviewer that is used to monitor HD/SD video and audio feeds for the TV side of the house.

Brockett would much rather manage a situation before it becomes a crisis downstream.

Making Sense of the Virtual StudioSMART STRATEGIES AND VIRTUAL TOOLS FOR ADAPTING TO CHANGE

Curious about how the modern studio has evolved in an IP world? Virtualization of the studio is WAY more than tossing a control surface on a touch screen. With today's tools, you can virtualize control over almost ANYTHING you want to do with your audio network. This free e-book illustrates what real-world engineers and radio studios are doing. Pretty amazing stuff.

Advancing AOIP for BroadcastTAKING ADVANTAGE OF EMERGING STANDARDS SUCH AS AES67 VIA AUDIO OVER IP TO GET THE MOST OUT OF YOUR BROADCAST FACILITY

Putting together a new studio? Updating an existing studio? This collection of articles, white papers, and brand new material can help you get the most out of your venture. Best of all, it's FREE to download!

IP Audio for TV Production and Beyond

WHAT YOU NEED TO KNOW ABOUT MANAGING MORE CHANNELS, MORE MIXES, AND MORE REMOTE VENUES

For this FREE e-book download, we've put together this e-book with fresh info and some of the articles that we've authored for our website, white papers, and news that dives into some of the cool stuff you can do with a modern AoIP network like Wheatstone's WheatNet-IP.

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